Electron multipliers

Abstract

An apparatus for amplifying an electron signal caused by the impact of a particle with an electron emissive surface. The apparatus includes: a first electron emissive surface configured to receive an input particle and thereby emit one or more secondary electrons, a series of second and subsequent electron emissive surfaces configured to form an amplified electron signal from the one or more secondary electrons emitted by the first electron emissive surface, and one or more power supplies configured to apply bias voltage(s) to one or more of the emissive surfaces. The bias voltage(s) is sufficient to form the amplified electron signal. The apparatus is configured such that the terminal electron emissive surface(s) of the series of second and subsequent electron emissive surfaces draw a higher electrical current than that of the remainder electron emissive surface(s). The apparatus may be used as part of detector in a mass spectrometer, for example.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This Application is a Section 371 National Stage Application of International Application No. PCT / AU2017 / 050570, filed Jun. 8, 2017, published as WO 2017 / 210741 A1 on Dec. 14, 2017, in English, which is based on and claims the benefit of U.S. Provisional Patent Application No. 62 / 347,713, filed Jun. 9, 2016; the contents of which are hereby incorporated by reference in their entireties.FIELD OF THE INVENTION[0002]The present invention relates generally to components of scientific analytical equipment. More particularly, the invention relates to apparatus and methods for achieving high linear output currents from an electron multiplier.BACKGROUND TO THE INVENTION[0003]In many scientific applications, it is necessary to amplify an electron signal. For example, in a mass spectrometer the analyte is ionized to form a range of charged particles (ions). The resultant ions are then separated according to their mass-to-charge ratio, typically by ...

AI Technical Summary

Benefits of technology

The present invention provides an apparatus for amplifying an electron signal caused by the impact of a particle with an electron emissive surface. The apparatus includes a first electron emissive surface that receives the impact of the particle and emits secondary electrons. A series of second and subsequent electron emissive surfaces are provided that draw a higher electrical current than the remainder surfaces. The apparatus also includes one or more power supplies that apply bias voltages to the emissive surfaces. The bias voltages are sufficient to form the amplified electron signal. The apparatus can be used in various applications such as electron microscopy and impact detection.

Problems solved by technology

A problem in the art is that the voltage applied to a dynode may be perturbed from its optimum operating value when the dynode is subject to high output currents.

There are significant limitations with both of these methods for achieving high linear output currents from an electron multiplier.

In the case of using zener diodes, the temperature dependence of the zener voltage can be detrimental to the performance of the detector, and electrical noise generated by the zener diodes can interfere with low level signal measurements and may need to be suppressed.

Also the current flowing through the zener diode(s) and to the associated dynodes is limited by the resistors in series with the zener diodes, placing an upper limit on the detectors output signal current.

In the case of using a low resistance voltage divider to increase the bleed current (the current in the voltage divider chain), the heat generated in the electron multiplier by the power dissipated across the resistors of the resistive voltage divider can be significant and cause elevated background noise.

Also, this method requires the use of an expensive and relatively high power high voltage power supply.

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